Better bitrate and resolution normalization (#12644)

Jellyfin.Api/Helpers/StreamingHelpers.cs

@@ -219,11 +219,17 @@ public static class StreamingHelpers
                 }
                 else
                 {
+                    var h264EquivalentBitrate = EncodingHelper.ScaleBitrate(
+                        state.OutputVideoBitrate.Value,
+                        state.ActualOutputVideoCodec,
+                        "h264");
                     var resolution = ResolutionNormalizer.Normalize(
                         state.VideoStream?.BitRate,
                         state.OutputVideoBitrate.Value,
+                        h264EquivalentBitrate,
                         state.VideoRequest.MaxWidth,
-                        state.VideoRequest.MaxHeight);
+                        state.VideoRequest.MaxHeight,
+                        state.TargetFramerate);
 
                     state.VideoRequest.MaxWidth = resolution.MaxWidth;
                     state.VideoRequest.MaxHeight = resolution.MaxHeight;

MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs

@@ -2400,7 +2400,7 @@ namespace MediaBrowser.Controller.MediaEncoding
             return 1;
         }
 
-        private static int ScaleBitrate(int bitrate, string inputVideoCodec, string outputVideoCodec)
+        public static int ScaleBitrate(int bitrate, string inputVideoCodec, string outputVideoCodec)
         {
             var inputScaleFactor = GetVideoBitrateScaleFactor(inputVideoCodec);
             var outputScaleFactor = GetVideoBitrateScaleFactor(outputVideoCodec);
@@ -2424,6 +2424,12 @@ namespace MediaBrowser.Controller.MediaEncoding
             {
                 scaleFactor = Math.Max(scaleFactor, 2);
             }
+            else if (bitrate >= 30000000)
+            {
+                // Don't scale beyond 30Mbps, it is hardly visually noticeable for most codecs with our prefer speed encoding
+                // and will cause extremely high bitrate to be used for av1->h264 transcoding that will overload clients and encoders
+                scaleFactor = 1;
+            }
 
             return Convert.ToInt32(scaleFactor * bitrate);
         }

MediaBrowser.Model/Dlna/ResolutionNormalizer.cs

@@ -2,28 +2,33 @@
 #pragma warning disable CS1591
 
 using System;
+using System.Linq;
 
 namespace MediaBrowser.Model.Dlna
 {
     public static class ResolutionNormalizer
     {
-        private static readonly ResolutionConfiguration[] Configurations =
-            new[]
-            {
-                new ResolutionConfiguration(426, 320000),
-                new ResolutionConfiguration(640, 400000),
-                new ResolutionConfiguration(720, 950000),
-                new ResolutionConfiguration(1280, 2500000),
-                new ResolutionConfiguration(1920, 4000000),
-                new ResolutionConfiguration(2560, 20000000),
-                new ResolutionConfiguration(3840, 35000000)
-            };
+        // Please note: all bitrate here are in the scale of SDR h264 bitrate at 30fps
+        private static readonly ResolutionConfiguration[] _configurations =
+        [
+            new ResolutionConfiguration(416, 365000),
+            new ResolutionConfiguration(640, 730000),
+            new ResolutionConfiguration(768, 1100000),
+            new ResolutionConfiguration(960, 3000000),
+            new ResolutionConfiguration(1280, 6000000),
+            new ResolutionConfiguration(1920, 13500000),
+            new ResolutionConfiguration(2560, 28000000),
+            new ResolutionConfiguration(3840, 50000000)
+        ];
 
         public static ResolutionOptions Normalize(
             int? inputBitrate,
             int outputBitrate,
+            int h264EquivalentOutputBitrate,
             int? maxWidth,
-            int? maxHeight)
+            int? maxHeight,
+            float? targetFps,
+            bool isHdr = false) // We are not doing HDR transcoding for now, leave for future use
         {
             // If the bitrate isn't changing, then don't downscale the resolution
             if (inputBitrate.HasValue && outputBitrate >= inputBitrate.Value)
@@ -38,16 +43,26 @@ namespace MediaBrowser.Model.Dlna
                 }
             }
 
-            var resolutionConfig = GetResolutionConfiguration(outputBitrate);
-            if (resolutionConfig is not null)
+            var referenceBitrate = h264EquivalentOutputBitrate * (30.0f / (targetFps ?? 30.0f));
+
+            if (isHdr)
             {
-                var originvalValue = maxWidth;
+                referenceBitrate *= 0.8f;
+            }
 
-                maxWidth = Math.Min(resolutionConfig.MaxWidth, maxWidth ?? resolutionConfig.MaxWidth);
-                if (!originvalValue.HasValue || originvalValue.Value != maxWidth.Value)
-                {
-                    maxHeight = null;
-                }
+            var resolutionConfig = GetResolutionConfiguration(Convert.ToInt32(referenceBitrate));
+
+            if (resolutionConfig is null)
+            {
+                return new ResolutionOptions { MaxWidth = maxWidth, MaxHeight = maxHeight };
+            }
+
+            var originWidthValue = maxWidth;
+
+            maxWidth = Math.Min(resolutionConfig.MaxWidth, maxWidth ?? resolutionConfig.MaxWidth);
+            if (!originWidthValue.HasValue || originWidthValue.Value != maxWidth.Value)
+            {
+                maxHeight = null;
             }
 
             return new ResolutionOptions
@@ -59,19 +74,7 @@ namespace MediaBrowser.Model.Dlna
 
         private static ResolutionConfiguration GetResolutionConfiguration(int outputBitrate)
         {
-            ResolutionConfiguration previousOption = null;
-
-            foreach (var config in Configurations)
-            {
-                if (outputBitrate <= config.MaxBitrate)
-                {
-                    return previousOption ?? config;
-                }
-
-                previousOption = config;
-            }
-
-            return null;
+            return _configurations.FirstOrDefault(config => outputBitrate <= config.MaxBitrate);
         }
     }
 }